Method for Controlling an Imaging Beam Path Which is Tapped off From a Film Recording Beam Path of a Movie Camera

ABSTRACT

A method for controlling an imaging beam path which is tapped off from a film recording beam path of a movie camera and is interrupted periodically as a function of the image recording frequency of the movie camera is provided. The imaging beam path is interrupted at a constant or variable frequency by means of an optical switching element during the exposure phase of the movie film, or is deflected from a first imaging plane to at least one second imaging plane, or to a light trap. An apparatus comprising at least one DMD-chip which is arranged in the imaging beam path of the movie camera and has micromirrors which are arranged in the form of a raster, can be pivoted under electronic control, and deflect an incident beam path to a first or a second imaging plane, or into a light trap.

CROSS-REFERENCE TO A RELATED APPLICATION

This application is a National Phase Patent Application of InternationalPatent Application Number PCT/DE2005/000498, filed on Mar. 15, 2005,which claims priority of German Patent Application Number 10 2004 016224.7, filed on Mar. 26, 2004.

BACKGROUND

The invention relates to a method for controlling an imaging beam path,which is tapped off from a film recording beam path of a movie cameraand to an apparatus for carrying out the method.

DE 27 34 792 C2 discloses a viewfinder system for a movie camera havinga rotating mirror shutter which is synchronized to the transport speedof a movie film, periodically interrupts the recording beam path, whichruns from a recording objective of the movie camera to the film planeand branches off into a viewfinder beam path, such that an image of thescene to be recorded is either alternately projected onto a movie filmin an exposure phase, or is diffracted from the rotating mirror shutterinto the viewfinder beam path in an exposure pause. An image plane islocated in the viewfinder beam path at the same distance from thereflective surface of the rotating mirror shutter as the film plane, onwhich image plane the viewfinder image is imaged in the exposure pauseby transmission optics as a real image on the plane of an image fieldshutter, and can be viewed through an eyepiece.

In order to allow the contrast scope of a recorded image to be assessedbetter and to allow scattered light as well as reflected light to beidentified more easily, it is known from pages 42 and 43 of theoperating instructions for the ARRIFLEX 535 movie camera for a moviecamera to be equipped with contrast filters which can be pivoted bymeans of a lever into the viewfinder beam path of a movie camera, thusmaking it possible to vary the quality of the viewing of the recordedimage in steps.

JP 10010633 A discloses a viewfinder arrangement for a still-imagecamera, in which a DMD (Digital Micromirror Device) chip is arranged inthe viewfinder beam path and has a large number of two-dimensionallyarranged micromirror elements, which comprise micromirrors which arearticulated such that they can move and digitally vary the deflectionangle when a voltage is applied, that is to say can be pivoted betweentwo different alignments of the mirror surface. The DMD chip, which isarranged in the viewfinder beam path, is driven by a DMD driver circuitand places either the recorded beams received via an objective or theinformation emitted from a display in the viewfinder beam path, so thatit is possible to view either an object to be recorded or the displayinformation using the viewfinder. The display and the driver circuitwhich drives the DMD chip are driven by a common CPU.

This known viewfinder system is, however, not suitable for overlayingformat indications on the viewfinder image of a movie camera or forsuperimposing or simultaneous overlaying of recording-specific orcamera-specific data in a viewfinder image together with the viewfinderbeam path, which is tapped from a recording beam path, since the displayinformation which is overlayed in the viewfinder beam path is input fromthe display, but is not governed by the position or deflection of themicromirrors.

It is also known for DMD chips to be driven with a changing frequency,so that the gray-scale levels for the light transmission by means of theDMD chip can be varied as a function of the ratio of the switched-ontimes to the switched-off times, that is to say a brighter gray-scalelevel is transmitted when the switched-on times are long in comparisonto the switched-off times, while darker gray-scale levels aretransmitted if the switched-off times are increased in comparison to theswitched-on times.

A further problem in the operation of movie cameras is that there is arisk of the introduction of stray light via the eyepiece and theviewfinder beam path into the movie camera and thus into the recordingbeam path, resulting in undesirable exposure of the movie film, when,for example, the eyepiece is not covered by the cameraman's eye. Inorder to prevent such inadvertent exposure of the movie film by means ofstray light, complex measures are required, which consume space.

SUMMARY

One object of the present invention is to specify a method of the typementioned in the introduction, by means of which the contrast of theviewfinder image can be infinitely variable, and which ensures that nostray light can reach the movie film even when the viewfinder eyepieceis not covered.

The solution according to the invention allows continuously variableadjustment of the image brightness and/or of the image contrast of aviewfinder image, and prevents stray light from reaching the movie filmin a movie camera via the viewfinder beam path, irrespective of whetherthe viewfinder is covered.

In particular, the solution according to the invention makes it possibleto use the optical capabilities of an optical switching element in theform of a DMD chip in order to view the image through the viewfinder ofa movie camera, in that it controls the amount of light which isdeflected into the eyepiece of a movie camera from the viewfinder beampath during pauses in the exposure of the movie film, and thus allowsboth better assessment of the amount of contrast in the recorded image,as well as making it easy to identify stray light and light reflections.Furthermore, if the optical switching element is driven such that it issynchronized to the image recording sequence of the movie camera, thismakes it possible to prevent stray light from entering the movie camera,and thus from reaching the movie film, via the viewfinder beam path.

Variation of the duty ratio of the deflection of the imaging beam pathto the various imaging planes makes it possible not only to infinitelyvariably adjust the contrast for image viewing through the viewfinder ofthe movie camera, but also to tap off an additional video beam path forviewing and recording of the recorded image on a video monitor or videorecorder, and to control the amount of light which is tapped off intothe video beam path.

In particular, the duty ratio for the deflection of the imaging beampath is varied by pulse-width-modulated control of the optical switchingelement.

The imaging beam path may either be deflected as the viewfinder beampath of the movie camera onto an image plane which can be viewed throughan eyepiece, or into a light trap, as a video beam path of the moviecamera to an optoelectronic transducer for conversion of the video beampath to video signals, or into a light trap and both into a viewfinderbeam path with an image plane, which can be viewed through an eyepiece,and into a video beam path with an optoelectronic transducer forconversion of the video beam path to video signals from the moviecamera, or into a light trap.

In order to prevent exposure of the movie film by stray light when theeye has been removed from the viewfinder of the movie camera or theviewfinder is not covered, the imaging beam path is either interruptedin synchronism with the exposure phase of the movie film, or isdeflected from the image plane to be viewed through the eyepiece intothe light trap. In addition to the infinitely variably adjustablecontrast filter, this provides an electronic closure in the viewfinderbeam path of a movie camera, which effectively prevents inadvertentexposure of the movie film by light which enters the cameras interiorvia the viewfinder beam path.

An apparatus for carrying out the method is characterized by at leastone DMD (Digital Micromirror Device) chip which is arranged in theimaging beam path of the movie camera and has a large number ofmicromirrors which are arranged in the form of a raster, can be pivotedunder electronic control, and deflect the incident beam path to a firstor a second imaging plane, or into a light trap.

The apparatus according to the invention results in an optical switchingelement which is in the form of a DMD chip being used as an infinitelyvariable contrast filter and stray-light filter. Furthermore, the DMDchip may be used as an optical switching element to prevent stray lightfrom entering the recording beam path, and to control the amount oflight which is input into a viewfinder beam path and/or into a videobeam path of a movie camera.

These functions are carried out in such a way that the micromirrors of afirst DMD chip reflect the imaging beam path alternately to imagingoptics in a viewfinder beam path, or into a beam path of a first lighttrap, and/or the micromirrors of a second DMD chip deflect the imagingbeam path alternately to a video beam path with an optoelectronictransducer for conversion of the video beam path to video signals, orinto a beam path of a second light trap.

In one embodiment, the imaging beam path is split via a beam splitterinto a viewfinder beam path and a video beam path, the micromirrors ofthe first DMD chip, which is arranged in the viewfinder beam path,reflecting the imaging beam path to the imaging optics in the viewfinderbeam path with an image plane which can be viewed through an eyepiece,or into the beam path of the first light trap, and the micromirrors ofthe second DMD chip deflecting the imaging beam path to the video beampath with an optoelectronic transducer for conversion of the video beampath to video signals, or into the beam path of the second light trap.

Alternatively, the beam splitter can be arranged between the first DMDchip and the viewfinder eyepiece, and can split the imaging beam pathinto a viewfinder beam path and a video beam path, with the micromirrorsof the first DMD chip for light control alternately reflecting theimaging beam path to the beam splitter or into the beam path of thefirst light trap.

In this embodiment variant, the micromirrors of a second DMD chip forlight control can deflect the video beam path to an optoelectronictransducer for conversion of the video beam path to video signals, orinto a beam path of a second light trap.

The DMD chip or chips is or are preferably driven via a driver circuitwhich is connected to a control circuit for the movie camera and for thevideo output mirror or mirrors. This not only makes it possible tocontrol the amounts of light which are input into the viewfinder beampath or into the video beam path, but also to control thesynchronization with the image recording frequency of the movie cameraand/or the video frequency of the video output mirror device.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features of the invention and of the advantages which can beachieved by the solution according to the invention will be explainedwith reference to exemplary embodiments, which are illustrated in thefigures, in which:

FIG. 1 shows a schematic illustration of a film recording and imagingbeam path of a movie camera with a DMD chip for deflection of theimaging beam path into the viewfinder beam path of the movie camera, orinto a light trap.

FIG. 2 shows a schematic illustration of a film recording and imagingbeam path of a movie camera with a beam splitter for deflection of theimaging beam path into a viewfinder beam path, and a video beam path,each having a DMD chip for light control.

FIG. 3 shows a schematic illustration of a film recording and imagingbeam path of a movie camera with a DMD chip for light control, and witha beam splitter for deflection of the imaging beam path into aviewfinder beam path and a video beam path.

DETAILED DESCRIPTION

FIG. 1 uses schematic outlines to show a movie camera 1 with a rotatingmirror shutter 3, which passes a recording beam path S1 which is passedvia a camera objective 2, to a movie film 10, which moves on a filmplane behind an image window 4, for film image exposure during anexposure phase, or periodically deflected into an imaging beam path S2.A fiber panel or a matt disk 5 which, for example, is in the form of aplanar-convex lens, is arranged in the imaging beam path S2 and islocated on the image plane, that is to say at the same distance from therotating mirror shutter 3, as the film plane, on which the movie film 10is transported intermittently.

The recorded image which is imaged on the matt disk or fiber panel 5 inthe exposure pauses of the movie film 10 is deflected by means of a DMDchip 6 either into a viewfinder beam path S3 or into a beam path S4which leads to a light trap 13. The DMD chip 6 has a large number oftilting micromirrors, which are arranged in the form of a raster ormatrix and can be driven quickly by means of a driver circuit 15, on asemiconductor substrate, which mirrors are pivoted, depending on thedrive, by the driver circuit 15 between two mirror positions, whichinclude an angle of, for example, 10 to 12 degrees. Because themicromirrors of the DMD chip 6 are arranged in the form of a raster ormatrix, each micromirror corresponds to one image pixel, so that animage code which is supplied to the DMD chip 6 from the driver circuit15 in order to drive the micromirrors initiates each individualmicromirror, and accordingly leaves it in the rest position, or deflectsit to a deflected position.

On the input side, the driver circuit 15 is connected to a controlcircuit 16, which is connected to an input keyboard, camera or imagerecording sensors, or part of a microprocessor of the movie camera 1 inorder to control the camera functions and processing of input data ordata recorded by sensors.

The viewfinder eyepiece 8 contains an adjusting disk 81 in the form of amatt disk or fiber panel, where a viewfinder image is imaged, and can beviewed by a cameraman's eye 12 via viewfinder optics 82.

The input field of the movie camera 1 contains a nominal-valuetransmitter or a control element, by means of which the time duration ofthe deflection of the imaging beam path S2 into the viewfinder beam pathlevel S3 during the exposure phase of the movie film 10, and thus theamount of light input into the viewfinder beam path S3, can be adjusted.This allows the cameraman to mask out stray-light influences and lightreflections in the recorded image and, in particular, to optimize thecontrast range in the recorded image, in which case the continuouslyvariable adjustment of the control element is associated withcontinuously variable variation of the duty ratio of the micromirrors ofthe DMD chip 6, by means of which the micromirrors are pivoted betweenthe viewfinder beam path S3 and the beam path S4 of the light trap 13.

The driver circuit 15 drives the DMD chip 6 in such a manner that,during the image exposure pause, the micromirrors of the DMD chip 6 arepivoted backward and forward at high frequency between the viewfinderbeam path S3 and the beam path S4 of the light trap 13, and the amountof light, which is input into the viewfinder beam path S3 on the onehand and into the beam path S4 of the light trap 13 on the other hand,in the imaging beam path S2 is varied infinitely variably by variationof the duty ratio, by means of pulse-width modulation.

In order to prevent the movie image 10 from being exposed by stray lightwhen the eye 12 has been removed from the eyepiece 8 or the viewfindereyepiece 8 is not covered, the DMD chip 6 is driven via the drivercircuit 15 by the control circuit 16 such that the viewfinder beam pathS3 is interrupted synchronously during the exposure phase of the moviefilm 10, so that, during the exposure phase of the movie film 10, themicromirrors of the DMD chip 6 deflect the imaging beam path S2 into thebeam path S4 of the light trap 13, and thus mask out the light beamsentering the movie camera 1 from the viewfinder optics 8.

The arrangement shown in FIG. 1 may analogously have a video outputmirror device 9 as shown in FIG. 2 added to it, whose object andfunction will be explained in more detail in the following text.

In a corresponding manner to the schematic illustration of a filmrecording beam path and imaging beam path shown in FIG. 1, FIG. 2 showsa movie camera 1 with a rotating mirror shutter 3, which passes on therecording beam path S1, which passes via a camera objective 2, either toa movie film 10, which moves on a film plane behind an image window 4,for film image exposure, or deflects it to an imaging beam path S2. Amatt disk 5, on which a recorded image is imaged during the exposurepauses of the movie film 10, as well as a beam splitter 13 are arrangedin the imaging beam path S2, with the beam splitter 13 splitting theimaging beam path S2 into a viewfinder beam path S3, and a video beampath S5.

The viewfinder beam path S3 is deflected by means of a first DMD chip 6,which is arranged in the viewfinder beam path S3, either into aviewfinder eyepiece 8 or into a beam path S4, which leads to a firstlight trap 13.

The first DMD chip 6 has a large number of micromirrors which can bedriven at high speed and are arranged in the form of a raster or matrix,and which are pivoted between two limit positions, which include anangle of, for example, 10 to 12 degrees.

The viewfinder eyepiece 8 contains an adjusting disk 81 in the form of amatt disk or fiber panel, where a viewfinder image is imaged and can beviewed via viewfinder optics 82 by a cameraman's eye 12.

A second DMD chip 7 is arranged in the video beam path S5, which issplit off from the imaging beam path S2, and likewise has a large numberof micromirrors which can be driven quickly and are arranged in the formof a raster or matrix, and are pivoted between two limit positions whichinclude an angle of, for example, 10 to 12 degrees, and which deflectsthe video beam path S5 either to a video output mirror device 9 or asthe beam path S6 to a second light trap 14.

The video output mirror device 9 contains video optics 91, a videosensor 92 which converts the optical image from the beam path S5 toimage signals, and video electronics 93, which produce video signalsfrom the image signals and emit them, possibly together with furthercontrol signals and data, to a personal computer, as well as receivingdata and control signals from the personal computer. Since the videobeam path S5 which is deflected from the imaging beam path S2 by meansof the beam splitter 11 is passed via the second DMD chip 7, therecorded image is laterally inverted in the beam path to the videooutput mirror device 9, so that electronic mirroring is carried out inthe video output mirror device 9, in order to reproduce the imagecorrectly.

The video electronics 93 offer the capability for connection of amonitor 94, on which the video images formed from the video signals canbe viewed directly on the movie camera 1.

Depending on the angular position of the rotating mirror shutter 3, therecording beam path S1 strikes the opening sector (bright sector) of therotating mirror shutter 3, and passes through the image window 4 to themovie film 10, which is guided in the film channel, there, duringtransportation of the movie film 10, the image window 4 is covered bythe mirror surface of the rotating mirror shutter 3, and the recordingbeam path S1 is deflected as the imaging beam path S2 onto the matt diskor fiber panel 5, from where the imaging beam path S2 is split via thebeam splitter 11 into the viewfinder beam path S3 and the video beampath S5. The viewfinder beam path S3, which falls on the first DMD chip6, is deflected via its micromirror either to the viewfinder eyepiece 8or as the beam path S4 to the first light trap 13.

The video beam path S5, which is derived from the beam splitter 11,falls on the second DMD chip 7, which deflects it either to the videooutput mirror device 9 or as the beam path S6 to the second light trap14. As a result of the periodic interruption in the recording beam pathS1, the video output mirror device 9 has predetermined for it not only amode select signal, which presets a desired exposure mode, but also ashutter index signal by the movie camera, which corresponds to therespective exposure conditions for the video beam path S5 and thus theexposure conditions on the video sensor 92.

FIG. 3 shows an alternative embodiment in which the beam splitter 11 isarranged between the first DMD chip 6 and the adjusting disk 81 for theviewfinder eyepiece 8, so that the imaging beam path S2 is eitherreflected into the combined viewfinder and video beam path S3 and S5,respectively, or to the first light trap 13. The amount of light whichis deflected into the viewfinder and video beam path S3 or S5,respectively, is in this embodiment the same and depends on the divisionratio of the beam splitter 11, which may also be provided with differentreflection areas or pass areas, thus ensuring that the image is viewedin a suitable manner through the eyepiece 8 and video output mirrorsystem.

In this embodiment, either the second DMD chip 7 may be omitted, so thatthe video beam path corresponds to the viewfinder beam path, or a secondDMD chip 7 is provided in conjunction with a second light trap 14, as inthe embodiment shown in FIG. 2.

1-16. (canceled)
 17. A method for controlling an imaging beam path,which is tapped off from a movie film recording beam path of a moviecamera and is interrupted periodically as a function of the imagerecording frequency of the movie camera, wherein the imaging beam pathis interrupted at a constant or variable frequency by means of anoptical switching element during an exposure phase of the movie film, oris deflected from a first imaging plane to at least a second imagingplane, or to a light trap.
 18. The method of claim 17, wherein a dutyratio of the deflection of the imaging beam path onto the imaging planesor into the light trap is varied.
 19. The method of claim 18, whereinthe imaging beam path is deflected on a pulse-width-modulated basis ontothe imaging planes or into the light trap.
 20. The method of claim 17,wherein the imaging beam path is deflected as a viewfinder beam path ofthe movie camera onto an imaging plane, viewable through an eyepiece, orinto the light trap.
 21. The method of claim 17, wherein the imagingbeam path is deflected as a video beam path of the movie camera to avideo output mirror device with an optoelectronic transducer forconversion of the video beam path to video signals, or into anotherlight trap.
 22. The method of claim 17, wherein the imaging beam path isdeflected via a beam splitter into a viewfinder beam path with an imageplane which can be viewed through an eyepiece, and into a video beampath with an optoelectronic transducer for conversion of the video beampath to video signals from the movie camera.
 23. The method of claim 17,wherein the imaging beam path is interrupted in synchronism with theexposure phase of the movie film.
 24. The method of claim 17, whereinthe viewfinder beam path is deflected in synchronism with the exposurephase of the movie film from the first imaging plane, which can beviewed through an eyepiece, to the first light trap.
 25. The method ofclaim 21, wherein the video beam path is deflected in synchronism withthe exposure phase of the movie film from the video output mirror deviceto said another light trap.
 26. An apparatus for carrying out a methodfor controlling an imaging beam path, which is tapped off from a filmrecording beam path of a movie camera and is interrupted periodically asa function of an image recording frequency of the movie camera, whereinthe imaging beam path is interrupted at a constant or variable frequencyby means of an optical switching element during the exposure phase of amovie film, or is deflected from a first imaging plane to at least asecond imaging plane, or to a light trap, comprising at least oneDMD-chip which is arranged in the imaging beam path of the movie cameraand has a plurality of micromirrors which are arranged in the form of araster, wherein said DMD chip is pivotable under electronic control, anddeflects the beam path to the first or the second imaging plane, or intoa light trap.
 27. The apparatus of claim 26, wherein the micromirrors ofa first DMD chip reflect the imaging beam path to imaging optics in aviewfinder beam path or into a beam path of the light trap.
 28. Theapparatus of claim 27, wherein the micromirrors of a second DMD chipreflect the imaging beam path into a video beam path with anoptoelectronic transducer for compression of the video beam path tovideo signals, or into a beam path of another light trap.
 29. Theapparatus of claim 28, wherein the imaging beam path is split via a beamsplitter into a viewfinder beam path and a video beam path, wherein themicromirrors of said DMD chip, which is arranged in the viewfinder beampath, reflect the imaging beam path to the imaging optics in theviewfinder beam path with an image plane which can be viewed through aneyepiece, or into the beam path of the light trap, and wherein themicromirrors of the second DMD chip deflect the imaging beam path to thevideo beam path by means of an optoelectronic transducer for conversionof the video beam path to video signals, or into the beam path of thesecond light trap.
 30. The apparatus of claim 26, further comprising abeam splitter which is arranged between the DMD chip and a viewfindereyepiece, and splits the imaging beam path into a viewfinder beam pathand a video beam path, wherein the micromirrors of the DMD chip reflectthe imaging beam path alternately to the beam splitter or into a beampath of the light trap.
 31. The apparatus of claim 30, wherein themicromirrors of a second DMD chip deflect the video beam path to anoptoelectronic transducer for conversion of the video beam path to videosignals, or into a beam path of a second light trap.
 32. The apparatusof claims 31, wherein at least one of said DMD chips is connected via adriver circuit to a control circuit for the movie camera.
 33. A methodfor controlling an imaging beam path which is tapped off from a filmrecording beam path of a movie camera comprising: interrupting saidrecording beam path at a frequency during an exposure phase of the film;and deflecting said recording beam path from a first imaging plane to asecond imaging plane.
 34. The method as recited in claim 33 whereininterrupting comprising interrupting said recording beam path at avariable frequency using an optical switching element.
 35. A moviecamera comprising: a first imaging plane; a second imaging planedifferent from the first imaging plane; and a DMD chip pivotablyarranged along an imaging beam path of said movie camera for deflectinga beam path which is tapped off from a film recording beam path to oneof the first and second imaging planes.